Flying With Proportional – Integral – Derivative Control

May 18, 2016 by Rud Merriam 24 Comments

Your quad-copter is hovering nicely 100 feet north of you, its camera pointed exactly on target. The hover is doing so well all the RC transmitter controls are in the neutral position. The wind picks up a bit and now the ‘copter is 110 feet north. You adjust its position with your control stick but as you do the wind dies and you overshoot the correction. Another gust pushed it away from target in more than one direction as frustration passes your lips: ARGGGHH!! You promise yourself to get a new flight computer with position hold capability.

How do multicopters with smart controllers hold their position? They use a technique called Proportional – Integral – Derivative (PID) control. It’s a concept found in control systems of just about everything imaginable. To use PID your copter needs sensors that measure the current position and movement.

The typical sensors used for position control are a GPS receiver and an Inertial ~~Management~~ Measurement Unit (IMU) made up of an accelerometer, a gyroscope, and possibly a magnetometer (compass). Altitude control would require a barometer or some other means of measuring height above ground. Using sensor fusion techniques to combine the raw data, a computer can determine the position, movement, and altitude of the multicopter. But calculating corrections that will be just right, without over or undershooting the goal, is where PID comes into play. Continue reading “Flying With Proportional – Integral – Derivative Control” →

The Art And Science Of Bending Sheet Metal

May 18, 2016 by Moritz Walter 50 Comments

A motor mount. A sturdy enclosure. A 43.7° bracket. The average hack requires at least one angled metal part, and the best tool to make one is still the good ol’ press brake. Bending parts requires a few extra thoughts in the design and layout of the flat patterns, so if you want to know about bend allowances, bend deduction and how to bend accurate parts even without a press, read on.

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Two Guys, A Hotel Room And A Radio Fire

May 13, 2016 by Gregory L. Charvat 45 Comments

Can you build a HF SSB radio transciever in one weekend, while on the road, at parts from a swap meet? I can, but apparently not without setting something on fire.

Of course the swap meet I’m referring to is Hamvention, and Hamvention 2016 is coming up fast. In a previous trip to Hamvention, Scott Pastor (KC8KBK) and I challenged ourselves to restore tube radio gear in a dodgy Dayton-area hotel room where we repaired a WW2 era BC-224 and a Halicrafters receiver, scrounging parts from the Hamfest.

Our 2014 adventures were so much fun that it drove us to create our own hacking challenge in 2015 to cobble together a <$100 HF SSB transceiver (made in the USA for extra budget pressure), an ad-hoc antenna system, put this on the air, and make an out-of-state contact before the end of Hamvention using only parts and gear found at Hamvention. There’s no time to study manuals, antennas, EM theory, or vacuum tube circuitry. All you have are your whits, some basic tools, and all the Waffle House you can eat. But you have one thing on your side, the world’s largest collection of surplus electronics and radio junk in one place at one time. Can it be done?

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Tools Of The Trade – Component Placing

May 10, 2016 by Bob Baddeley 34 Comments

Recently we started a series on the components used to assemble a circuit board. The first issue was on dispensing solder paste. Moving down the assembly line, with the paste already on the board, the next step is getting the components onto the PCB. We’re just going to address SMT components in this issue, because the through hole assembly doesn’t take place until after the SMT components have gone through the process to affix them to the board.

SMT components will come in reels. These reels are paper or plastic with a clear plastic strip on top, and a reel typically has a few thousand components on it. Economies of scale really kick in with reels, especially passives. If you order SMT resistors in quantities of 1-10, they’re usually $.10 each. If you order a reel of 5000, it’s usually about $5 for the reel. It is cheaper to purchase a reel of 10 kOhm 0603 resistors and never have to order them again in your life than it is to order a few at a time. Plus the reel can be used on many pick-and-place machines, but the cut tape is often too short to use in automated processes.

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Minimal MQTT: Building A Broker

May 9, 2016 by Elliot Williams 49 Comments

In this short series, we’re going to get you set up with a completely DIY home automation system using MQTT. Why? Because it’s just about the easiest thing under the sun, and it’s something that many of you out there will be able to do with material on-hand: a Raspberry Pi as a server and an ESP8266 node as a sensor client. Expanding out to something more complicated is left as an exercise to the motivated reader, or can be simply left to mission creep.

We’ll do this in four baby steps. Each one should take you only fifteen minutes and is completely self-contained. There’s a bunch more that you can learn and explore, but we’re going to get you a taste of the power with the absolute minimal hassle.

In this installment, we’re going to build a broker on a Raspberry Pi, which is the hub of your MQTT network. Next time, we’ll get an ESP8266 up and running and start logging some data. After that, we’ll do some back-end scripting in Python to make the data speak, and in the last installment, we’ll explore some of the useful frills and fancy bits. Let’s get started!

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Which Wireless Tech Is Right For You?

May 5, 2016 by Bob Baddeley 43 Comments

It seems these days all the electronics projects are wireless in some form. Whether you choose WiFi, Bluetooth Classic, Bluetooth Low Energy, ZigBee, Z-Wave, Thread, NFC, RFID, Cell, IR, or even semaphore or carrier pigeon depends a lot on the constraints of your project. There are a lot of variables to consider, so here is a guide to help you navigate the choices and come to a conclusion about which to use in your project.

We can really quickly reduce options down to the appropriate tech with just a few questions.

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Analog To Digital Converter (ADC): A True Understanding

May 5, 2016 by Bil Herd 65 Comments

Back in the day where the microprocessor was our standard building block, we tended to concentrate on computation and processing of data and not so much on I/O. Simply put there were a lot of things we had to get working just so we could then read the state of an I/O port or a counter.

Nowadays the microcontroller has taken care of most of the system level needs with the luxury of built in RAM memory and the ability to upload our code. That leaves us able to concentrate on the major role of a microcontroller: to interpret something about the environment, make decisions, and often output the result to energize a motor, LED, or some other twiddly bits.

Often the usefulness of a small microcontroller project depends on being able to interpret external signals in the form of voltage or less often, current. For example the output of a photocell, or a temperature sensor may use an analog voltage to indicate brightness or the temperature. Enter the Analog to Digital Converter (ADC) with the ability to convert an external signal to a processor readable value.